The present disclosure relates to the thermal insulation of a battery enclosure and, for example, to an insulation of an enclosure containing battery cells that is exposed to high temperatures during operation.
Battery powered tools have provided increased convenience and productivity to medical professionals in surgical settings. These surgical tools and their associated batteries are sterilized before utilization, such as in the sterile field of an operating room. Battery powered surgical tools are typically designed to withstand the temperatures associated with an autoclave cycle for sterilizing a surgical tool or instrument. These temperatures may reach, for example, 132° C. for several minutes in a pre-vacuum sterilizer or 121° C. for 30 minutes or longer in a gravity displacement sterilizer.
Like the surgical tools and instruments, the battery enclosures of such tools are also sterilized. This sterilization presents a problem as the performance of rechargeable battery cells can be degraded if they are exposed to temperatures in excess of 70° C. Beyond degraded performance, the battery cells themselves are at risk of being permanently damaged upon exposure to temperatures in excess of 80° C.
One approach to prevent the battery cells from reaching such critical temperatures has been to sterilize the battery enclosure without the battery cells. The battery cells are then added to the enclosure with the use of shields and sealable covers to prevent exposure of the cells to the sterile field. Another approach has been to insulate the battery cell with the use of insulation materials, such as microporous silicate (U.S. Pat. No. 6,756,766) or silica (silicon dioxide) or silica ceramic carbon nitride and silica aerogel (U.S. Pat. No. 8,486,560).
Yet another approach has been to use chemicals and gasses to sterilize the battery enclosure with the battery cells. This type of sterilization process avoids generating temperatures that could potentially damage the battery cells. However, this approach requires sterilization infrastructure not typically present in hospitals, surgery centers and other healthcare institutions.